Power plant and system for accelerating a cross compound turbine in such plant, especially one having an HTGR steam supply

Abstract

An electric power plant having a cross compound steam turbine and a steam source that includes a high temperature gas-cooled nuclear reactor. The steam turbine includes high and intermediate-pressure portions which drive a first generating means, and a low-pressure portion which drives a second generating means. The steam source supplies superheat steam to the high-pressure turbine portion, and an associated bypass permits the superheat steam to flow from the source to the exhaust of the high-pressure portion. The intermediate and low-pressure portions use reheat steam; an associated bypass permits reheat steam to flow from the source to the low-pressure exhaust. An auxiliary turbine driven by steam exhausted from the high-pressure portion and its bypass drives a gas blower to propel the coolant gas through the reactor. While the bypass flow of reheat steam is varied to maintain an elevated pressure of reheat steam upon its discharge from the source, both the first and second generating means and their associated turbines are accelerated initially by admitting steam to the intermediate and low-pressure portions. The electrical speed of the second generating means is equalized with that of the first generating means, whereupon the generating means are connected and acceleration proceeds under control of the flow through the high-pressure portion.

What is claimed is: 
     
       1. A power plant comprising, a steam source to generate superheat and reheat steam;   a cross compound turbine-generator including, a high pressure turbine portion operated by a first flow of superheat steam, an intermediate turbine portion operated by a second flow of reheat steam, and a first electrical generating means rotatably driven by said high and intermediate pressure turbine portions, and a second electrical generating means rotatably driven by a low pressure turbine portion operated by the second flow after it is exhausted from the intermediate pressure portion;   first bypass means for conducting a flow of superheat steam from said steam source to a steam exhaust of said high pressure turbine portion;   second bypass means for conducting a flow of reheat steam from said steam source to a steam exhaust of said low pressure turbine portion; and   control means for independently governing the first and second flows, wherein one of the first and second flows is varied for purposes of controlling the rotational speed of said first electrical generating means in accordance with a desired value of such speed, while the other of the first and second flows is varied to regulate a power plant variable in accordance with its desired value.   
     
     
       2. A power plant according to claim 1 further comprising means for passing an equalizing steam flow through said low pressure turbine portion in order to increase the rotational speed of said second electrical generating means at times when the rotational speed of said first electrical generating means is effectively constant. 
     
     
       3. A power plant according to claim 2 further comprising means for electrically connecting said first and second electrical generating means when their rotational speeds are effectively equal. 
     
     
       4. A power plant according to claim 1 wherein said steam source includes a high-temperature gas-cooled nuclear reactor and a steam generator to produce the superheat and reheat steam using heat derived from the coolant gas of said reactor. 
     
     
       5. A power plant according to claim 4 wherein an auxiliary steam turbine means is connected to use steam that is generated by said steam source for driving a means for circulating the coolant gas through said reactor and said steam generator. 
     
     
       6. A power plant according to claim 5 wherein said auxiliary steam turbine means uses steam that is exhausted from said high-pressure turbine portion and said first bypass means. 
     
     
       7. A power plant according to claim 1 wherein the first steam flow is constant while the second steam flow is varied for speed control at times when the rotational speed of said first electrical generating means is less than a distinct value. 
     
     
       8. A power plant according to claim 7 wherein the constant level of the first steam flow is zero. 
     
     
       9. A power plant according to claim 7 wherein the first steam flow is varied for speed control at times when the rotational speed of said first electrical generating means exceeds the distinct value. 
     
     
       10. A power plant according to claim 9 wherein the second steam flow is varied to maintain a desired pressure of steam in the first stage of said intermediate pressure turbine portion at times when the first steam flow is varied for purposes of speed control. 
     
     
       11. A power plant according to claim 10 wherein the desired value of the first stage pressure is the value of such pressure at the time of commencement of variation of the first flow for speed control purposes. 
     
     
       12. A power plant according to claim 10 wherein the level of the first steam flow is zero at times when the second steam flow is varied for speed control purposes. 
     
     
       13. A power plant according to claim 1 wherein said control means include a governor valve means and a throttle valve means in series connection with said governor valve means, said governor valve and throttle valve means being connected to control the first steam flow, said governor valve means being positioned to vary the first steam flow at times when the rotational speed of said first electrical generating means exceeds a distinct value, and said throttle valve means being positioned to vary the first steam flow at times when such rotational speed is less than the distinct value. 
     
     
       14. A power plant according to claim 13 wherein one of said governor valve and throttle valve means is held fully open at times when the other of such valve means is positioned to vary the first steam flow. 
     
     
       15. A system for controlling the rotational speed of a turbine-generator, said turbine-generator having a first turbine portion rotatably coupled to drive a first electrical generating means and a second turbine portion rotatably coupled to drive a second electrical generating means, said turbine portions being connected to a steam supply such that a first flow of steam passes through a high-pressure section of said first turbine portion and a second flow of steam passes through an intermediate pressure section of said first turbine portion and through said second turbine portion so that the first and second flows may differ in level, said system comprising, a source to generate a reference value of the rotational speed of said first turbine portion,   a detector to detect the rotational speed of said first turbine portion and to generate a representation of the detected speed, and   means responsive to the reference and detected speed values for controlling the first and second flows, wherein one of the first and second flows is varied to regulate the detected rotational speed according to its desired value, that one of the first and second flows which is not used for speed regulation being held substantially constant or varied to regulate a variable associated with said turbine-generator and its steam supply according to a desired value of such variable.   
     
     
       16. A system according to claim 15 wherein that one of the first and second flows which is not used for speed regulation is zero at times when it is substantially constant. 
     
     
       17. A system according to claim 15 wherein the second steam flow is varied for purposes of speed regulation at times when the rotational speed of said first turbine portion is less than a distinct value. 
     
     
       18. A system according to claim 17 wherein the first flow is zero at times when the rotational speed of said first turbine portion is less than the distinct value. 
     
     
       19. A system according to claim 15 wherein the second flow is varied to regulate a detected pressure of steam within the intermediate pressure section of said first turbine portion according to a desired value of such pressure at times when the first flow is varied to regulate the rotational speed of said first turbine portion. 
     
     
       20. A system according to claim 15 further comprising, means for passing a third steam flow through said second turbine portion at times when it is desired to equalize the electrical speeds of said first and second generating means, and wherein said means for controlling varies the third steam flow to increase the electrical speed of said second generating means until such speed is equal to the electrical speed of said first generating means. 
     
     
       21. A system according to claim 20 wherein the second flow is varied for purposes of holding the electrical speed of said first generating means constant at times when the third flow is varied to equalize the electrical speeds of said first and second electrical generating means. 
     
     
       22. A system according to claim 21 wherein the first flow is zero at times when the electrical speeds are equalized. 
     
     
       23. A system according to claim 21 wherein the rotational speed of first turbine portion is held constant at a distinct value at times when the electrical speeds of said first and second generating means are equalized, the first steam flow being varied for purposes of regulating the rotational speed of said first generating means when such speed exceeds the distinct value. 
     
     
       24. A system according to claim 23 wherein the level of the third flow is zero at times when the rotational speed of said first turbine portion is regulated by varying the first flow. 
     
     
       25. A system according to claim 23 wherein the second flow is varied to maintain a desired value of the pressure of steam within the intermediate pressure section of said first turbine portion at times when the first flow is varied for purposes of speed regulation. 
     
     
       26. A system according to claim 25 wherein the desired value of the steam pressure within the intermediate pressure section is the value of such pressure at the time the electrical speeds of said first and second generating means are equalized. 
     
     
       27. A system according to claim 15 wherein said steam supply includes means for passing a fourth flow of steam around the intermediate pressure section of said first turbine portion and said second turbine portion to the exhaust of said second turbine portion, and further comprising, means for detecting a pressure of steam at a point in said steam supply such that the first and second flows pass through such point, and for generating a representation of the detected steam pressure, and wherein said means for controlling varies the fourth flow to regulate the detected pressure according to a desired value thereof.   
     
     
       28. A system according to claim 27 wherein the desired value of the regulated steam pressure is such that the sum of the second flow with the fourth flow is equal to a desired minimum flow at times when the second flow is less than the desired minimum. 
     
     
       29. A system according to claim 28 wherein the level of the desired minimum flow is equal to the level of the second flow at times when the combined power output of said first and second generating means is equal to a predetermined distinct value.